338 



ORGANOGRAPHY. 



or coriaceous, or when the interior of its cells is much thickened 

 by secondary deposits it assumes various degrees of hardness, 

 and may become woody, crustaceous, &c. 



The surface of the testa, also presents various appearances, and 

 is often furnished with different appendages. Thus it may be 

 smooth or glabrous, as in the Adenanthera ; or wrinkled, as in 

 Niyella ; striated, as in Tobacco; marked with ridges and furrows, 

 as in Delphinium (fig. 728) ; netted, as in Nasturtium {fig. 726); 

 alveolate or pitted, as in the Poppy (fig. 727); tuberculated, as 

 in Chickweed (fig. 729); spiny, as in the Mulberry, &c. The 

 testa of some seeds is also furnished with hairs, which may either 

 cover the entire surface, as in various species of Gossypium, 

 where they constitute the material of so much value, called 

 Cotton, and in the Silk-cotton tree (Bombax); or they may be 

 confined to certain points of their surface, as in the Willow 

 (fig. 733), Asclepias (fig. 732), Apocynum, and Epihhium 

 (fig. 738); in the latter cases the tufts of hairs thus formed, con- 



Fig. 730. Fig. 731. Fig. 732. Fig, 733. 



Fig. 730. Seed of a species of Pinu.i, with a winged appendage, w. 



Fig.Til. Marginate or bordered seed of Sandwort (Are- 



naria) Flg.l'A'i. Coinose o\a\ %t^^ of Asclepias. .— Fig. 



Comose seed of a species of Willow. 



stitute what is called a coma, and the seed is said to be comose. 

 The hairs thus found upon the surface of seeds facilitate their 

 dispersion by the wind. Other seeds again, have winged appen- 

 dages of various kinds, which also render them buoyant and 

 facilitate their dispersion; thus in the Sandwort (Arenaria) (fig. 

 731), the testa is prolonged, so as to form a winged margin to 

 the seed, wliich is then described as maryinufe or bordered ; in the 

 seeds of the Pinus (fig. 730), Catalpa, Bigno/iia, Swietenia, 

 Moringa, Sec, the testa forms wings, and the seed is winged. 

 These winged seeds must be carefully distinguished from saina- 

 roid fruits, such as the Ash, Elm, Sycamore, Sic, where the 

 wing is an exjjansion of the pericarp instead of the seed. In like 



